Scraper assemblies which are pulled along the bottoms of sedimentation or sewage basins to push accumulated sediment into troughs or the like for expeditious removal are generally known in the art. It is also known to provide suction assemblies continuously to remove the sediment piled up in front of advancing scraper blades. A system of the latter type is disclosed in U.S. Pat. No. 2,052,676 in which the scraper blade and suction assembly revolve in a continuous circular path about the central axis of a round settling tank. As will be appreciated, in a round tank, the scraper blade can maintain engagement with the bottom of the tank, or basin, at all times.
On the other hand, in a sediment removal system for a rectangular basin, in which the scraper is reciprocated between the ends of the basin, it is desirable to maintain the scraper blade in engagement with basin bottom only during movement in one direction, namely, during the sediment collecting pass. The system must therefore be provided with means for elevating the scraper blade above the basin bottom during the return pass of the blade.
Just such a system is disclosed in U.S. Pat. No. 1,918,742 in which horizontal rails having pivoting sections are provided along the sides of the basin in order to engage and elevate the scraper blade above the bottom of the basin during the return pass. Although this system is operable, it is relatively costly since rails must be provided along the entire length of the basin.
Still other installations utilize an overhead shuttle railway from which is suspended a sediment collector which travels to and fro on the basin floor. The disadvantage of this type of system is that if tube settlers are used, one or more interruptions, such as slots or spaces, must be provided in the tube settlers throughout the entire length of the basin to accommodate the travel of the collector-supporting member.
In short, there remains considerable room for improvement in the art.